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post #1 of (permalink) Old 05-15-2007, 01:58 PM Thread Starter
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Gauges - Mechanical or Electrical?

I'm getting ready to order the remaining gauges for my CJ...Engine and tranny temp and the Vacuum.

I can get either mechanical or electrical...the mechanical gauges appeal to me because of the simplicity and better chance of accuracy....however, I'm kinda concerned with the interface...i.e., the connection. With electrical you just screw in the sending unit and you are now free to run the signal wire anyway you want. With the mechanical I'm assuming that the sending unit and gauge will be a combined unit....hence, not as easy to unplug things...not to mention, 'maybe' more prone to damage.

Opinions?

Or maybe I should say 'Input?'...cuz we all know that everyone here has plenty of 'opinions'......

AKA DDawg16
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
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post #2 of (permalink) Old 05-15-2007, 02:37 PM
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Mechanical temperature gauges are a single unit. You have to order them by length. There's a bulb that screws into the engine, a long brass tube, and then the meter. It has to be installed by passing the bulb and tube through the panel, through the firewall and into the engine. It is kind of a pain.

Pressure gauges don't have a sending unit; just a tube that runs between the meter and the pressure source. The tube can be disconnected at both ends and replaced. They commonly use a very small, maybe 1/8" OD, polyethelene tube which is easy to route and pretty tough. Years ago the plastic would get brittle after several years of service and eventually crack. It doesn't seem to be much of a problem any more.

What I like about mechanical gauges is that it's quite common to get them with a 270 degree needle movement, where most electrical gauges have 90 degree movement. It's a lot easier to get a quick idea of the reading when all you need to do is glance at the angle of the needle.

EVERYTHING's easy for the guy who doesn't have to do it.
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post #3 of (permalink) Old 05-15-2007, 08:07 PM
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What Jim said is right on the money.

But, i still like an electric gauge better. Just easier to run copper wires then a plastic tube or that PITA bulb for the water temp.

The last street rod i helped put together we ran both sets of guages. The electric was in the dash and the manual ones were just wiretied under the hood. We did that to get a good actual reading and to double check the electric guages. The electric guages were right on the money. But they were very pricey units. So they better have been right on.

Even with cheap electric guages. Once you now where the motor runs then it it really just a check point at that time. If the guage is off by 5 lbs of pressure. It doesnt really matter, cause it will always be off by that 5 lbs. And if it dropped off you know you have a problem.

As for a vacum guage. WHY? Just something else to watch and make you nervous if it is off. IF the motor is running right, then you have vacum. If it is running like crap then you probably dont have it.

What????
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post #4 of (permalink) Old 05-15-2007, 11:19 PM
 
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I've been a race car builder for too long, I won't use anything but mechanical gauges when possible.
Just too reliable.
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post #5 of (permalink) Old 05-15-2007, 11:23 PM
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For a CJ that see's lots of of the trail.. I favor electric... there's a whole lot of twisting going on and I just don't trust that capaliary tube. I've had them fracture and it's never fun. IMHO, on the trail, their a showstopper point of failure.
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post #6 of (permalink) Old 05-16-2007, 12:35 AM
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Electric 100%. Having an oil pressure tube break is an experience I could have gone a lifetime without. I have used both VDO and Autometer gauges in my Jeeps and hot rods, without any inaccuracy issues or failures. They're not cheap, but you get what you pay for. I've never tried the "low end" electrical gauges...

You can get electrical gauges with full-sweep dials. They're not cheap, though.

I like the idea of dash mounted electrical units, and under-hood mechanical units. Saves you from having to keep going back to look at the dash while working under the hood. Might try that on my next project.

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post #7 of (permalink) Old 05-16-2007, 12:40 AM
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I choose to mix them, I have always run a mech. vacuum gauge, great for timing and monitoring performance and engine condition and a mech OP gauge, the tubing is far more tuffer than the past, protect it when nessecary.
Temp gauge usually is ele. with a tee at the source for a mech. gauge
my .02

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post #8 of (permalink) Old 05-16-2007, 10:33 AM Thread Starter
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Thanks guys....that was the input I wanted....and you basically confirmed what I suspected.

While I like the reliability of the mechanical, I'm going electric....and mainly because of the harsh driving off road. CA is mostly rock and that just beats the crap out of the jeep.....(one of my reasons for getting rid of the poly bushings)...

The vacuum gauge will be mechanical..no brainer there....and I'm going to use Thor's trick for air pressure to the locker...he has a pressure switch that lights up a light on his dash when he has enough air pressure on the locker line. I'll just mount a small pres gauge under the hood near the compressor.

Well....won't be doing much to the jeep this weekend....I'll be with you guys killing a few brain cells.....see you guys tomorrow night.

AKA DDawg16
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
D44 Flat top in progress...
Link to my Frame up Restore
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